Study On The RFID Antennas In Complex Target Environment

RFID radio frequency identification technology is an automatic identificationtechnology developing rapidly in recent years. Due to the advantage the traditionalautomatic identification technology does not have, this technology is widely applied tothe fields like defense, production, life, logistics and so on. With the expansion ofapplication fields, RFID is facing higher and higher practical standards. The applicationin complex environments (especially the metal objects, liquid environment, etc) and theminiaturization of the tag antennas become research hotspots. The main work of thispaper will focus on the anti-metal design and the miniaturization of UHF band RFIDantennas.Taking Electromagnetic simulation software HFSS as an auxiliary tool, theresearch of RFID tag antenna and reader antenna mainly about the miniaturization andanti-metallization of tag antenna and the compact design of reader antenna are carriedout.A new anti-metal tag antenna which include a antenna body and a director hasdesigned. Using the basic principle of Yagi antenna guiding the electromagnetic waves,a capacitive grid-like metal layer structure as the director is placed above the antennapatch. This structure can guide the electromagnetic waves the antenna radiated spreadover the tag, and thus weaken or eliminate the adverse effects owning to the reflectionof electromagnetic waves from the metallic surface. After physical processing and tests,this method proves to have good performance on metallic objects. Also a compact andanti-metal tag antenna based on the circular patch antenna is designed. Utilizing themeander technology, some slots is cut on the antenna patch, effectively increasing theequivalent electrical length of the antenna; and a short to ground structure is set near thefeed, weaking the impact of items back, meanwhile, further reducing the physical sizeof the antenna. After analysis, these two tag antennas realize good anti-matal properties.And a miniaturzation improved reader antenna based on a commercial antenna isdesigned. Though optimization of the antenna size, the antenna maintains a high gainwhile getting a size reduction of nearly a third compared with the original antenna. The sample processed achieved a good performance after actual test.